Modern aircraft have a plurality of control surfaces, systems, actuators, torques, temperatures, and the like which need to be monitored to ensure proper operation of the aircraft In order to be able to monitor the various aircraft parameters, sensors are used on the individual control surfaces, actuators, and engines to detect the various parameters. The values detected by the sensors can subsequently be employed for instrumentation, used to generate control commands, and for various diagnostics. With diagnostic applications, the values detected by the sensors may be compared with predetermined values for a given parameter under selected conditions and a malfunction can be identified in the event a deviation is detected by the respective sensor from the predetermined values.
A variety of sensors may be employed depending on the application. Rotary or Linear Variable Differential Transformer sensors (RVDT or LVDT sensors), synchros and resolvers are conventionally used as sensors in aircraft because they are very robust with respect to external disturbances and have simple construction. However, in other applications potentiometers and some low-level sensors are also commonly employed. Unfortunately, such sensors are commonly not as robust, and may be more susceptible to external disturbances and, because of their low signal levels, offsets and biases in signal processing circuitry.
When sensors are used to detect various aircraft parameters, the sensors used must typically be monitored to ensure error free operation. Failures of sensors, and/or the wiring harness, or interfaces to sensors impact system reliability and result in a need for redundancy and overdesign to ensure operation. It is also desirable to ensure that potential failures are not only detectable, but also, preferably relegated to lesser importance and minimized impact on system reliability. Therefore, it is desirable to have a simplified sensor interface where potential failures such as open circuits in the sensor or wiring are detectable or mitigated, or both, such that their impact is not significant.